Device for stripping a product substrate from a carrier substrate

ABSTRACT

Device for stripping a product substrate from a carrier substrate connected to the product substrate by an interconnect layer by means of a flexible film that is mounted on a film frame and that comprises an adhesive layer for holding the product substrate in a bonding surface section of the film, the film being mounted on the film frame in an attachment section of the film that surrounds the bonding surface section, and the film comprising a stripping section that is located between the bonding surface section and the attachment section, the device having stripping means for effecting a stripping of the product substrate from the carrier substrate from a periphery of the product substrate.

RELATED APPLICATIONS

The present application is a divisional of U.S. application Ser. No.14/013,145, filed Aug. 29, 2013, which is a divisional of U.S.application Ser. No. 13/392,123, filed Feb. 24, 2012 (now U.S. Pat. No.8,894,807, issued Nov. 25, 2014), which is a U.S. National StageApplication of International Application No. PCT/EP2010/005108, filedAug. 20, 2010, which claims priority from European Patent ApplicationNo. 09011198.0, filed Sep. 1, 2009, said patent applications herebyfully incorporated herein by reference.

FIELD OF THE INVENTION

The invention relates to a device and a method for stripping a productsubstrate from a carrier substrate.

BACKGROUND OF THE INVENTION

The back-thinning of product substrates is often necessary in thesemiconductor industry and can take place mechanically and/orchemically. For purposes of back-thinning, in general the productsubstrates are temporarily fixed on a carrier, there being variousmethods for the fixing. The carrier material can be, for example, films,glass substrates or silicon wafers.

Depending on the carrier materials used and the interconnect layer usedbetween the carrier and the product substrate, different methods fordissolving or destroying the interconnect layer are known, such as, forexample, the use of UV light, laser beams, the action of temperature, orsolvents.

Stripping increasingly constitutes one of the most critical processsteps since thin substrates with substrate thicknesses of a few micronseasily break during stripping/peeling or are damaged by the forces thatare necessary for the stripping process.

Moreover, thin substrates have hardly any stability of shape or none atall and typically curl without support material. During handling ofback-thinned wafers, therefore, fixing and support of the wafers areessentially indispensable.

SUMMARY OF THE INVENTION

Therefore, the object of this invention is to devise a device and amethod to detach such a product substrate from a carrier in asnondestructive a manner as possible.

This object is achieved with the features of the independent claims.Advantageous further developments of the invention are given in thedependent claims. The framework of the invention also encompasses allcombinations of at least two of the features given in the specification,the claims, and/or the figures. In the specified value ranges, valuesthat lie within the indicated limits will also be disclosed as boundaryvalues, and they are to be claimed in any combination.

The invention is based on the idea of further developing a genericdevice and a generic method by the elasticity or flexibility of a filmmounted on a film frame being used to carefully strip the productsubstrate starting from the edge of the product substrate namely bydeforming the film, especially in a stripping section of the film. Inthis way, the product substrate is immediately available for otherprocess steps directly after separation and is protected by the film andthe film frame. Many process steps can be carried out directly on theproduct substrate mounted on the film frame.

In other words: the flexible film by means of a force bordering the filmframe and the adhesive layer that bonds the product substrate in thebonding surface section of the film delivers a tensile force to theproduct substrate, by which the product substrate is stripped,especially peeled, from the carrier substrate.

A product substrate is defined as a product substrate, for example asemiconductor wafer, which is conventionally thinned to a thickness ofbetween 0.5 μm and 250 μm am, the trend being toward thinner and thinnerproduct substrates. This invention works especially effectively withproduct substrates that themselves have flexibility similar to the filmmounted on the film frame. In the device according to the invention andthe method according to the invention, the product substrate is peeledfrom the carrier substrate, especially proceeding concentrically fromthe periphery of the product substrate.

The carrier is, for example, a carrier substrate with a thickness ofbetween 50 μm and 5,000 μm, especially between 500 μm and 1,000 μm.

The interconnect layer can be an adhesive, for example a solubleadhesive, especially a thermoplastic, which is applied, for example,selectively in an edge region of the carrier substrate-product substratecombination, especially in an edge zone of from 0.1 to 20 mm.Alternatively, the adhesive can be applied over the entire surface, andthe adhesive force can be reduced in the center by an adhesion-reducinglayer, for example a fluoropolymer, preferably Teflon.

A chuck is especially well suited as the holding means, especially aspinner chuck for holding the carrier substrate, especially by means ofnegative pressure, for example suction paths, holes or suction cups.Alternatively, mechanical holding, for example by lateral clamps, isconceivable. Holding takes place electrostatically in anotheralternative configuration.

The stripping means encompass the film mounted on the film frame and afilm frame holder that applies a force and that holds the film frame.

Advantageously, in addition to the stripping means, there is aconnection release means for at least partial release of the connectionbetween the carrier substrate and the product substrate caused by theinterconnect layer.

To the extent that the device has heating means for heating the carriersubstrate-product substrate combination that are integrated especiallyinto the carrier substrate holder, a thermoplastically melting adhesivecan be used as an interconnect layer. The maximum heating temperature is250° C., preferably a maximum 175° C.

In one advantageous embodiment of the invention, it is provided that theconnection release means is made to work essentially without heating. Inthis way, it is possible to omit any heating means.

In another advantageous embodiment of the invention, it is provided thatthe connection release means comprises fluid means, especially a solventthat selectively dissolves the interconnect layer, for detaching theinterconnect layer. Chemical dissolution of the interconnect layer isespecially protective of the product substrate and with thecorresponding material choice, dissolution can also take place veryquickly, especially when only edge regions of the product substrate areprovided with an interconnect layer, so that the solvent can act veryquickly from the side. In this way, perforations in the carriersubstrate and/or product substrate can be omitted.

In one alternative embodiment of the invention, it is provided that theconnection release means comprises mechanical separating means,especially a blade for cutting through the interconnect layer, fordetaching the interconnect layer. In this way, especially promptseparation of the product substrate from the carrier is possible. Acombination of mechanical separating means and fluid means is alsoconceivable.

In another alternative embodiment of the invention, it is provided thatthe connection release means comprises a UV light source for detachingthe interconnect layer. This embodiment can also be combined with theembodiment of the mechanical separating means and/or the embodiment withfluid means.

To the extent that the connection release means is made to actespecially exclusively from one side edge of the product substrate,action on the product substrate and/or the carrier from the top and/orbottom, especially the inside region of the product substrate that lieswithin the side edge, can be omitted.

There being a rotation means for rotation of the carrier substrate,product substrate and/or film frame with the film makes it possible toomit an arrangement of the connection release means over the entireperiphery of the product substrate and partial action on the peripheryof the product substrate is sufficient.

To the extent that the stripping section is located outside of the outercontour of the product substrate and/or adjoins the bonding section,optimum transfer of the stripping force to the product substrate ispossible by deformation of the film.

Advantageously, to expose the interconnect layer to the fluid means, forholding the fluid means there is a solvent reservoir that is fastened,especially sealed, to the carrier substrate or carrier substrate holder,the top edge of the reservoir extending at least as far as the planeformed by the product substrate. The solvent reservoir at leastpartially encompassing the side edge or the periphery of the productsubstrate allows especially effective action on the interconnect layer.Furthermore, the measure of encompassing prevents fluid means fromescaping from the solvent reservoir or UV light intensity from beinglost. When using mechanical separation means, possible contaminants areprevented from escaping from the solvent reservoir and contaminating theproduct substrate. The solvent reservoir can be made L-shaped orU-shaped in cross-section in one advantageous configuration.

In another advantageous configuration of the invention, it is providedthat the solvent reservoir extends only over one peripheral sector ofthe side edge or the periphery of the product substrate. Advantageously,the solvent reservoir extends only slightly over the side edge orperiphery of the carrier substrate or product substrate in the directionof the product substrate center so that a force Fs can be applied to thecarrier substrate. The force Fs can also be transferred to the carriersubstrate via the solvent reservoir.

According to one advantageous embodiment of the invention, it isprovided that stripping results by a force Fs that acts on the carriersubstrate and a force Ff that acts on the film frame and that isdirected against the force Fs. The device can be made to deliver theforce Ff as a local force, especially in spots at at least one point onthe film frame. Advantageously, the force Ff is delivered distributedamong several points on the periphery of the film frame, wherebydifferent forces can also be delivered and tilting of the film framerelative to the carrier substrate or the carrier substrate holder can becaused by the device.

A uniform force distribution on the periphery of the product substratedepending on the desired form of stripping is achieved by the capacityof the film to be deformed, especially stretched, by the force Fs andthe force Ff in the stripping section.

According to another advantageous embodiment of the invention, it isprovided that the force Fs and the force Ff can cause displacement ofthe film frame relative to the carrier substrate, whereby in this waywithin the film frame a trough being formed that has acoustic wavegenerating means, especially formed from a fluid that can be held in thetrough and an acoustic transmitter immersed in the fluid, fortransmission of acoustic waves to the product substrate and/or thesolvent. The stripping of the product substrate is greatly acceleratedby the cavitation generated by ultrasound or megasound so that thestripping takes place much more carefully and at the same time morerapidly.

Advantageously, it is furthermore provided that the stripping of theproduct substrate takes place concentrically from the periphery of theproduct substrate to the center of the product substrate.

It is especially advantageous if the product substrate is made to adhereto the film during the stripping process since in this way, blanketholding and protection are ensured.

Other advantages, features and details of the invention will becomeapparent from the following description of preferred embodiments andbased on the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a shows a schematic top view of a substrate combination consistingof the product substrate, the carrier substrate and the interconnectlayer on a film frame,

FIG. 1b shows a schematic side view to FIG. 1a with a detailed view,

FIG. 2 shows a schematic representation of the device according to theinvention in the stripping of the product substrate from the carriersubstrate with a detailed view,

FIG. 3 shows a schematic representation of the device according to theinvention in the stripping of the product substrate from the carriersubstrate with a detailed view,

FIG. 4 shows a schematic representation of one embodiment of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

In the figures, the same components and components with the samefunction are identified with the same reference number.

FIG. 1a shows a film frame 1 that is round in this embodiment at leaston an inner periphery 1 i, with a film 3 mounted, especially glued, onits bottom. With a radial distance to the inner periphery 1 i of thefilm frame 1, within the film frame 1 a product substrate-carriersubstrate combination is glued on an adhesive layer 3 s of the film 3concentrically to the film frame 1 (see FIG. 1b ).

The product substrate-carrier substrate combination consists of aproduct substrate 4 that adheres to the film 3, a carrier substrate 2,and an interconnect layer 6 that connects the product substrate 4 andthe carrier substrate 2. The diameters of the product substrate 4 and ofthe carrier substrate 2 are essentially identical, while the thicknessof the product substrate 4 is less than the thickness of the carriersubstrate 2.

The film 3 consists of an attachment section 3 b that has the shape of acircular ring in this case and in which the film 3 is fixed to the filmframe 1. Furthermore, the film 3 consists of a bonding surface section 3k in which the product substrate 4 can be fixed on the adhesive layer 3s of the film 3. Between the attachment section 3 b and the bondingsurface section 3 k, there is a stripping section 3 a that is locatedespecially concentrically to the attachment section 3 b and the bondingsurface section 3 k, and that has a function that is critical accordingto the invention. The stripping section 3 a thus extends from aperiphery 4 u of the product substrate 4 to the inner periphery 1 i ofthe film frame, here labeled distance A. The ratio between a thickness Dof the film frame 1 and the distance A is advantageously at least 1 to 2to 1 to 50, especially 1 to 5 to 1 to 25, and preferably 1 to 19 to 1 to10.

In the initial position shown in FIG. 1b , the side of the productsubstrate 4 that makes contact with the film 3 and the side of the filmframe 1 that makes contact with the film 3 are arranged flush in oneplane E. The parts shown in FIGS. 1a and 1b are assembled on a knownfilm frame mounter.

FIGS. 2 and 3 schematically show the stripping process in two variants,namely shortly after the start of the stripping of the product substrate2 from the carrier substrate 4.

By delivering opposing forces Ff, or Ff1 and Ff2, and Fs, the productsubstrate-carrier substrate combination and the bonding surface section3 k of the film 3, which section adheres to the combination, are movedout of the film frame 1 in the direction of a carrier substrate holder7. In a kinematic reversal, the film frame 1 can also be moved by theforce Ff by means of a film frame holder that is not shown, for examplea robot arm.

The force is transferred from the carrier substrate holder 7 to thecarrier substrate 2 via vacuum paths 8 that have been machined into thesurface of the carrier substrate holder 7 and via a vacuum means that isconnected to them and that is not shown. The carrier substrate holder 7is anchored securely to the device.

Alternatively, the holding of the carrier substrate 2 can take placemechanically, for example by clamping, or electrostatically.

The force Ff acting on the film frame 1—as shown in FIG. 2—can actuniformly distributed as a superficial force on the film frame 1 so thatthe stripping of the product substrate 4 from the carrier substrate 2takes place from the edge by way of deformation of the stripping section3 a, as is shown enlarged in the detailed representation in FIG. 2. Theforce Ff1 is identical here to the force Ff2. The force can be deliveredin spots distributed on the periphery of the film frame 1 or can beintroduced distributed by a film frame holder.

In the embodiment shown in FIG. 3, the force distribution on theperiphery of the film frame 1 is different, specifically the force Ff1is greater than the force Ff2 on the opposite side so that the productsubstrate 4 is stripped first on the side on which the greater force Ff1is delivered. The holding means for delivering the force into the filmframe 1 must therefore be made to allow tipping of the film frame 1.

The product substrate 4 promotes stripping since it behaves in anelastic manner that is similar to the film 3 and is thus detached fromthe product substrate-carrier substrate combination step by step fromits edge.

According to FIG. 4, the solvent reservoir 20 is arranged on the carriersubstrate 2 such that immersion of the product substrate-carriersubstrate combination in the position of the product substrate-carriersubstrate combination exposed to a force is enabled. The solventreservoir 20 is attached annularly in this case to the periphery of thecarrier substrate 2, especially to form a seal, so that the force can bedelivered, as before, within the solvent reservoir 20 to the carriersubstrate 2. The force can also be delivered alternatively to thesolvent reservoir 20, for example when the solvent reservoir 20 isattached nonpositively to the carrier substrate 2. An outer peripheralwall 21 of the solvent reservoir 20 extends at least as far as a planeformed by the product substrate 4 so that the solvent 22 in the solventreservoir 20 reaches at least as far as the interconnect layer 6, andthe latter can be dissolved by the solvent 22. Advantageously, the outerperipheral wall 21 extends beyond the plane formed by the productsubstrate 4 almost as far as the film frame 1 so that even duringrotation, escape of the solvent 22 from the solvent reservoir 20 isavoided as much as possible.

This measure supports stripping, especially peeling of the productsubstrate 4 from the carrier substrate 2, by the interconnect layer 6being dissolved from the periphery 4 u of the product substrate 4 andthe product substrate 4 being carefully lifted by the tensile forceapplied to the periphery 4 u deforming the film 3.

The deformation of the film 3 causes a trough 9. The delivery of a fluid11 into the trough 9 is made for transmission of acoustic waves(ultrasound, megasound) via the film 3 into the solvent 22 locatedopposite the film 3 and into the product substrate-carrier substratecombination by means of an acoustic wave generating means, here anacoustic transmitter 10. The solvent 22 acts in an accelerated manner onthe interconnect layer 6 by the delivery of sound from the edge so thatthe return force of the film 3 in the direction of the film frame 1 canbe reduced and/or stripping is supported, especially for radiallysymmetrical stripping according to FIG. 2.

The delivery of sound causes the molecules of the solvent 22 to vibrate,resulting in cavitation; this leads to distinct acceleration of thedissolution of the interconnect layer 6.

The solvent 22 is advantageously matched selectively to the interconnectlayer 6, and the adhesive layer 3 s cannot be attacked by the solvent22.

REFERENCE SYMBOL LIST

-   A Distance-   D Thickness-   E Plane-   1 Film frame-   1 i Inner periphery-   2 Carrier substrate-   3 Film-   3 a Stripping section-   3 b Attachment section-   3 k Bonding surface section-   3 s Adhesive layer-   4 Product substrate-   4 u Periphery-   6 Interconnect layer-   7 Carrier substrate holder-   8 Vacuum paths-   9 Trough-   10 Acoustic transmitter-   11 Fluid-   20 Solvent reservoir-   21 External peripheral wall-   22 Solvent

Having described the invention, the following is claimed:
 1. Device forat least partially detaching a semiconductor wafer from a carriersubstrate wherein a connecting layer is disposed between a planarsurface of the semiconductor wafer and an opposite-facing planar surfaceof the carrier substrate, said connecting layer for bonding thesemiconductor wafer to the carrier substrate, said device comprising: aflexible film having an upper surface and a lower surface, the flexiblefilm including a bonding surface section on the lower surface, anadhesive layer disposed on the bonding surface section for holding thesemiconductor wafer to the bonding surface section of the flexible film,an attachment section on the lower surface of the flexible film whereinthe attachment section surrounds the outer periphery of the bondingsurface section and a stripping section located between the bondingsurface section and the attachment section; a film frame mounted to theflexible film at the attachment section; a delivery device configured toapply a fluid only to a periphery of the connecting layer for at leastpartial dissolution of the connecting layer; a stripping deviceconfigured to strip the semiconductor wafer from the carrier substratefrom the periphery of the semiconductor wafer to a center of thesemiconductor wafer by applying a first force to the carrier substrateand a second force to the film frame, the first force acting in adirection generally opposite to a direction of the second force, whereinthe bonding surface section of the flexible film is positioned below thefilm frame and the upper surface of the flexible film forms a trough forreceiving a second fluid; and a sound wave generator disposed in saidtrough formed by said flexible film and immersed in said second fluid,said sound wave generator configured to expose the connecting layer tosound waves for accelerating the rate that the semiconductor wafer isdetached from the carrier substrate.
 2. Device for at least partiallydetaching a semiconductor wafer from a carrier substrate wherein aconnecting layer is disposed between a planar surface of thesemiconductor wafer and an opposite-facing planar surface of the carriersubstrate, said connecting layer for bonding the semiconductor wafer tothe carrier substrate, said device comprising: a flexible film having anupper surface and a lower surface, the flexible film including a bondingsurface section on the lower surface, an adhesive layer disposed on thebonding surface section for holding the semiconductor wafer to thebonding surface section of the flexible film, an attachment section onthe lower surface of the flexible film wherein the attachment sectionsurrounds the outer periphery of the bonding surface section and astripping section located between the bonding surface section and theattachment section; a film frame mounted to the flexible film at theattachment section; a delivery device configured to apply a fluid onlyto a periphery of the connecting layer for at least partial dissolutionof the connecting layer; a stripping device configured to strip thesemiconductor wafer from the carrier substrate from the periphery of thesemiconductor wafer to a center of the semiconductor wafer by applying afirst force to the carrier substrate and a second force to the filmframe, the first force acting in a direction generally opposite to adirection of the second force, wherein the bonding surface section ofthe flexible film is positioned below the film frame and the uppersurface of the flexible film forms a trough for receiving a secondfluid; a sound wave generator disposed in said trough formed by saidflexible film and immersed in said second fluid, said sound wavegenerator configured to expose the connecting layer to sound waves foraccelerating the rate that the semiconductor wafer is detached from thecarrier substrate; and a rotation device configured to rotate thecarrier substrate, the connecting layer and the semiconductor waferwhile exposing the connecting layer to the fluid, the connecting layerhaving a side edge disposed perpendicular to a planar surface of thesemiconductor wafer wherein, at each instance of time during rotation, aportion of the side edge of the connecting layer is in contact with thefluid and another portion of the side edge of the connecting layer isnot in contact with the fluid.
 3. Device for at least partiallydetaching a semiconductor wafer from a carrier substrate wherein aconnecting layer is disposed between a planar surface of thesemiconductor wafer and an opposite-facing planar surface of the carriersubstrate, said connecting layer for bonding the semiconductor wafer tothe carrier substrate, said device comprising: a flexible film having anupper surface and a lower surface, the flexible film including a bondingsurface section on the lower surface, an adhesive layer disposed on thebonding surface section for holding the semiconductor wafer to thebonding surface section of the flexible film, an attachment section onthe lower surface of the flexible film wherein the attachment sectionsurrounds the outer periphery of the bonding surface section and astripping section located between the bonding surface section and theattachment section; a film frame mounted to the flexible film at theattachment section; a delivery device configured to apply a fluid onlyto a periphery of the connecting layer for at least partial dissolutionof the connecting layer; a stripping device configured to strip thesemiconductor wafer from the carrier substrate from the periphery of thesemiconductor wafer to a center of the semiconductor wafer by applying afirst force to the carrier substrate and a second force to the filmframe, the first force acting in a direction generally opposite to adirection of the second force, wherein the bonding surface section ofthe flexible film is positioned below the film frame and the uppersurface of the flexible film forms a trough for receiving a secondfluid; and a sound wave generator disposed in said trough formed by saidflexible film and immersed in said second fluid, said sound wavegenerator configured to expose the connecting layer to sound waves foraccelerating the rate that the semiconductor wafer is detached from thecarrier substrate, wherein the connecting layer is a glue that isdisposed only at an outer peripheral edge of the planar surface of thecarrier substrate and at an outer peripheral edge of a planar surface ofthe semiconductor wafer facing the carrier substrate.
 4. Device fordetaching a semiconductor wafer from a carrier substrate wherein aconnecting layer is disposed between a lower surface of thesemiconductor wafer and an upper surface of the carrier substrate, anupper surface of the semiconductor wafer being attached to a centralportion of a bottom surface of a film, the device comprising: a flexiblefilm having an upper surface and a lower surface, the flexible filmincluding a bonding surface section on the lower surface, an adhesivelayer disposed on the bonding surface section for holding thesemiconductor wafer to the bonding surface section of the flexible film,an attachment section on the lower surface of the flexible film whereinthe attachment section surrounds the outer periphery of the bondingsurface section and a stripping section located between the bondingsurface section and the attachment section; a film frame mounted to theflexible film at the attachment section; a delivery device configured toapply a first fluid only to a periphery of the connecting layer for atleast partial dissolution of the connecting layer; a stripping deviceconfigured to strip the semiconductor wafer from the carrier substratefrom the periphery of the semiconductor wafer to a center of thesemiconductor wafer by applying a first force to the carrier substrateand a second force to the film frame, the first force acting in adirection generally opposite to a direction of the second force, whereinthe carrier substrate and the central portion of the film is movedrelative to an outer peripheral edge of the film such that the centralportion of the film is positioned below the outer peripheral edge of thefilm and the upper surface of the film defines a trough region of thefilm; a second fluid disposed in the trough region defined by the uppersurface of the film; and a sound wave generator disposed in said troughregion formed by said flexible film and immersed in said second fluid,said sound wave generator configured to introduce sound waves into thesecond fluid in the trough region such that the sound waves aretransmitted into the first fluid to accelerate the rate that thesemiconductor wafer is separated from the carrier substrate.